1. Field of the Invention
The present invention relates to a method of and an apparatus for applying a light beam to a sheet such as a photographic film, a stimulable phosphor sheet, or the like to scan the sheet.
2. Description of the Related Art
There is known a system for recording radiation image information of a subject such as a human body with a stimulable phosphor, and reproducing the recorded radiation image information on a photosensitive medium such as a photographic film, or displaying the recorded radiation image information on a display device such as a CRT or the like.
The stimulable phosphor is a phosphor which, when exposed to an applied radiation (X-rays, xcex1-rays, xcex3-rays, electron beams, ultraviolet radiation, or the like), stores a part of the energy of the radiation, and, when subsequently exposed to applied stimulating rays such as visible light, emits light in proportion to the stored energy of the radiation. Usually, a sheet provided with a layer of the stimulable phosphor is used as a stimulable phosphor sheet and stored in a cassette in the art.
The above known system includes an image information reading apparatus (scanning apparatus) which comprises a reading unit (scanning unit) for reading the recorded radiation image information from the stimulable phosphor sheet, and an erasing unit for erasing remaining image information from the stimulable phosphor sheet after the recorded image information has been read. The image information reading apparatus operates as follows: A cassette housing a stimulable phosphor sheet with radiation image information which has been recorded therein by an external exposure device is inserted into a loading unit of the image information reading apparatus. When the lid of the cassette is opened, the stimulable phosphor sheet is removed from the cassette by a suction mechanism, and then fed to the reading unit by a sheet feeding mechanism (sheet feeder). After the recorded image information is read from the stimulable phosphor sheet by the reading unit, the stimulable phosphor sheet is delivered to the erasing unit where any remaining radiation image information is erased from the stimulable phosphor sheet. The stimulable phosphor sheet is then returned into the cassette in the loading unit.
The above system also includes an image information reproducing apparatus (scanning apparatus) for reproducing radiation image information on a photographic photosensitive medium such as a photographic film or the like. The image information reproducing apparatus has a magazine which contains a plurality of photographic photosensitive mediums. In operation, one of the photographic photosensitive mediums at a time is removed from the magazine and delivered to a sheet feeding mechanism (sheet feeder), which feeds the photographic photosensitive medium to a recording unit (scanning unit). In the recording unit, the radiation image information obtained from the stimulable phosphor sheet is recorded on the photographic photosensitive medium.
In the image information reading apparatus and the image information reproducing apparatus, when a sheet-like member such as the stimulable phosphor sheet or the photographic photosensitive medium is fed to the scanning unit such as the reading unit or the recording unit by the sheet feeding mechanism, the sheet feeding mechanism needs to release the sheet-like member in order to allow only an auxiliary scanning feed means of the scanning unit to feed the sheet-like member highly accurately in an auxiliary scanning direction. Since the sheet feeding mechanism has a roller pair for nipping the sheet-like member while it is feeding the sheet-like member, a nip releasing mechanism is required to release the roller pair from the sheet-like member when the sheet-like member is transferred from the sheet feeding mechanism to the auxiliary scanning feed means. However, the nip releasing mechanism makes the apparatus complex in structure and results in a considerable increase in the cost of the apparatus.
It is a major object of the present invention to provide a method of and an apparatus for scanning a sheet-like member highly accurately with a simple and inexpensive arrangement without the need for a special mechanism for releasing the sheet-like member from a gripping action of a feeder.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example.